The yellow sticker usually correspond to what tote they belong in and the order they're in for the delivery route, first thing you typically do is unpack a tote in the truck and sort them by number for ease of access.

My brain wants to trigger this sorting mode whenever I grab my packages, and it just reminds me of that terrible job.

Amazon has a system of desperate contractor companies that are absolutely reliant on amazon since they own the warehouses, trucks, and everything, but are also a moment away from having their contract ended, basically destroying the company. As a result you're not really respected even if your employer tries hard to, they just can't care for employees at risk of dissolving.